Aeronautical propeller



Dec. 9, 1924.- 1,518,410

S. A. REED AERONAUT I CAL PROPELLER Filed June 22. 1922 26' i0 INVENTOR. j I

'BY g I W1.IQWUML ATTORNEY 1 Patented Dec. 9, 1924.

UNITED STATES PATENT SILVANUS ALBERT REED, OF NEW YORK, N. Y., ASSIGNOR TO THE REED PEOPELLEJH;

00., INC., 01 NEW YORK, N.Y., A COBPGRA'IION OF NEW YORK.

AnnoNAUrIcAL, rnornnztnn Application filed June 22,1922. Seria1 1ioit70,139.

' To all whom it may concern: air resistance. While the centrifugal force Be it known'that I, SrnvANUs Annnnr issufiicient to supply the necessary rigidity REED, a citizen of the United States, and against axial and tangential flexure to the 5p resident of New York, in the county of thin sharp outer portions of the blades, yet New .York and State of New York, have the rigidity of the blades against change of invented certain new and useful Improvepitch is maintained, there 1s needed a corments in Aeronautical Propellers, of which rect adjustment of the weight of material the following is a specification. to dimensions and form at the successive m This invention relates generally to problade cross-sections. When using a heavy In pellers for aeronautical use and particularly metal this is d-iflicult unless the blades are to Ipropellers of the metal type. made hollow, which is objectionable and n my Patent No. 1,463,556, granted July has not proved satisfactory in practice. 31, 1923, I have described and claimed. a. When solid, the blades must, with heavy my new and improved type of aeronautical prometal, be-made ofa thinness graduated at peller which includes among other features all sections which though possible of adthe use of metal as a material from which justment to flying conditions is close to the to form the propeller. The main reason border line of practicability. Reference indicated in said patent for specifying was made in 111 said patent to the use of 7 metal depended upon the fact that, as the aluminum, a light-weight metal, as a factor superiority of the propeller disclosed was in obtaining the desired lightness of condue mainly to its thin sharp blades, esstruction, and; the present application, pecially in their outer and more rapidly which is in large part a-division or conmoving portions, and as such thinness 'tinuation of said patent, particularly in m wouldvbe relatively devoid of structural or eludes, among other features, a propeller 5 intrinsic rigidity, the invention therein deformed of relatively light-weight metal of scribed included the making of the propelsufficient strength. ler of metal and relying largely upon cenv I have discovered that an alloy of alumitrifugal force to supply the necessary renum which'is nearly as light as the latter sistance to flexnre. Vith such thinness and and which has in additionphysical propflexibility .of the outer portions of the erties similar to steel, possesses the qualiblades, was associated an increase in crossties which enable me to give to the relativel section and corresponding intrinsic rigidity thin blades a suflicient thickness to furnis I progressively towards the axis of rotation. structural ri idity with an ample margin e increase in the present invention in to support e pitch twist at a constant cross-section being so proportioned at vafigure, and yet not reach a prohibitive rious parts that, while still maintaining a, weight, while, at the same time affording relative thinness of the inner se-ctions, the enough centrifugal force to provide kinetic outer and more flexible portions are sup- -or virtual rigidity to the outer parts of W ported and maintained in operative angles the blades sufiicient to minimize flexure and 40 and positions for the necessary thrust, in still preserve the thinness and, sharpness conjunction with the use of a light-weight which is an important feature of the invenmetal of high tensile strength as being estion. I, therefore, prefer to use alloys of pecially adapted to such. purpose. this character, such as duralumin or even as The effect of centrifugal force, while lighter alloys of other metals provided they favorable to resistance of the blade to forhave similar physical properties and are ward and tangential fiexure' under the insufiiciently elastic and non-brittle, also maluence of air resistance, may be unfavorable leable and flexible, and have the necessary to permanence of the longitudinal twist tensile strength. With such physical propice given to the blades to give them the desired erties and a weight not exceeding oi helical pitch, and to maintain this twist a'pound per cubic inch, I am able to make constant, the intrinsic rigidity ofthe blade solid propellers with an ample margin be must be suflic'ient to resist the-influence of tween the limits of bulk and, weight to operate with superior efficiency and yet not exceed. or substantially exceed, the weight of a wooden propeller for the. same service.

My propeller is made of a light and strong metal and preferably in a single piece and without hollow spaces, welds. rivets or joints. and is not only of superior efficiency in that it makes possible the use of thin sharp blades. but is superior to wooden propellers and hollow metal propellers in permanence and resistance to wear and tear of service.

In my said patent hereinbefore referred to, I have obtained the central reversal of blade angle by a compound bend equivalent to a twist of the flat plate from which the propeller was formed and I used shaftattaching'blocks, shaped to the contour of the central bends which had as one function to assist in maintaining the blade against straightening out under the pull of centrifugal force. I have discovered that with proper dimensions, shape and character of material of the propeller, such as the aluminum or similar alloys mentioned, the

shaft-attaching blocks may be dispensed with and the set or rigidity of the material may be relied upon to maintain the central bends or twists constant, so that for attachment to the driving-shaft only a flange at the end of the shaft is necessary and to which the propeller is screwed or bolted, or otherwise attached. Such flange may be of varying form and either integral with the shaft or attached thereto by a sleeve or tubular extension keyed to the shaft, and the flange may be flat with filler-blocks interposed to fit the curved contour of the propeller, or the flange may be itself curved to so fit the propeller contour.

It is tobe noted that the relatively wide and relatively thin central region of my propeller affords the maximum efliciency for transmission of the torque of the drive-shaft relatively to the mass of material. I have also found that the central reversal of blade angle can be safely made by a simple twist of the wide flat central zone of the propeller, and I prefer such simple twist, as it brings the working or useful region of the blade closer in towards the axis of rotation and thereby lengthens the operative bladesurface. Such twist may be made while the metal is cold and the resultant blade angles varied at will, by again twisting'to a ermanent set, and with the aluminum a loy mentioned, this may be done many times without weakening the blades.

In my said patent, I also describe a onepiece hub-less propeller of resilient metal having the blades integral with each other, and with the main part of each blade shown as substantially of uniform width, that is to say, with theleading and the trailing edges of the blade parallel for the greater part of the length of the blade. As this prolonged parallelism of the blade edges is less favorable to the desired inter-relation of cross-sections before referred to. Iavoid this by making the blade of a tapering formation in both thickness and width starting from or near the central region of the structure and running to the blade-tip.

Like the form of blade in my said patent the present form tapers in thickness from at or near the central part of the propeller to the blade-tip, and this characterizes the present form with the peculiarity of having something of a proportioned and interrelated taper in width and thickness.

I have found from actual flights of airplanes equipped with propellers embodying my inventions, that an efficient speed of propeller rotation can be attained far beyond the velocity of rotation of propellers heretofore known which required the gearing down of the engine speeds to suit these restricted capabilities. I am, therefore, able to effectively utilize speeds in which the tip veloclties of the propeller are equal to and even greater than the velocity of sound, with corresponding efficiencies and other advantages resulting thereform.

Certain forms of my improved propeller and certain preferred methods of constructing the same are hereinafter described and set forth and illustrated in the drawings; wherein Fig. 1, is a side View of a propeller embodying my invention.

Fig. 2, is a front view of the propeller shown in Fig. 1.

Fig. 3, is a central longitudinal section of the propeller shown in Figs. 1 and 2, with shaft attaching means added thereto.

Fig. 4, is a series of cross-sectional views taken on planes at different points of the length of the propeller.

Fig. 5, is a side view of the central portion of the propeller, with a shaft passing through the same and a shaft-attaching device mounted in place.

Fig. 6, is a side view of a portion of the shaft, an attaching device for securing the propeller to the shaft, the device being shown with a flange shaped to conform to the contacting faceof the propeller.

Fig 7, is a side view of the central portion of the propeller and a portion of the shaft, with an attaching device having a conforming flange placed on opposite sides of the propeller.

Fig. 8, is a similar View to Fig. 1, of a modified form of propeller.

Fig. 9, is a front view of the propeller shown in Fig. 8, together with the shaft attaching device.

Figs. 10 and 11, show side views of the central part of propellers shown in Figs.

8 and 9, and also attaching means in modified forms.

Referring to the drawings, in-Figs. 1 to 4, is shown a propeller formed of a single piece of metal, with tips 5 and 6 having a thickness of one-fourth to one-eighth of an inch or less, and 7 to 8 being central Qattach ing region of angle reversal and having a thickness of about one half to one inch, the thickness of each blade tapering from said central part 7-8, to the tips 5 and'6. The width of the blades also preferably de creases from the central part 7-8, to the tips 5 simple twist of the center part 7-8, to bring the section at 7, to an angle with the section at 8, usually of about ninety degrees. From 7 to 5 and from 8 to 6, the blades are then twisted each in the opposite direction from the first twist, so that the angle of the various sections indicated at a, b, c, e, f, and g, in Fig. 4:, with the plane of the propeller rotation, or radial plane, diminishes towards the tips more or less in accordance with the well known helical law for the pitch desired. At each of the sections a, b, 0, e, f, and g, the forward face is curved and the rear face more or less flat, and both .edges of the blades are sharp. The sections at c, and

e, are nearly flat on both sides and are sharpened at the edges and the section at d, is flat'with rounded edges. A hole 10, is formed at the center of the part 7-8, of the propeller for receiving the drive-shaft 11, to which the propeller is securely attached by means of a tubular member 12,

' having a peripheral outwardly extending fl'ange 13, for engaging the face of the propeller. The attaching flange is provided with a set of bolt-holes 14, which register with a corresponding set of holes 15, in the propeller, and suitable bolts 16, are placed through the registering holes for binding the parts together. While I show in Figs. 1 to 7, onlytwo bolt-holes for securing the parts together, of course, more bolt-holes may be used. A suitable key 17, is used for locking the shaft and the tubular member 12, together, and takes into keyways formed in said respective parts, and the usual nut arrangement inay be used to retain the propeller from moving forward on the drive-shaft. The. attachingflange 13, may be flat and non-conformed to the contacting face of the propeller, as shown in Fig. 5, but I prefer to shape its contacting surface so as to completely conform to fit the face of the propeller, as shown in Figs. 6 and 7 and thereby make a close and reinforcing contact with the central part of the propeller and the blades, the said flange being preferably elongated in the direction of length of the propeller, in the forms shown in Figs. 1 to 7. In the and 6, respectively. 9 denotes a.

In Figs. 8, 9, 10, 11, I show a variation in the construction of the propeller in which a virtual twist in the central part 7-8, for bringing the sections at those points to the required angle with the plane of rotation, is accomplished by a compound bend at 18-19, and 20-21, these bends being in opposite directions and at angles 18 with 19, and 20 with 21. and each cxtending entirely across the propeller and the pair 18-19, being symmetrical with the pair 20-21. There are various combinations of bends which will accomplish the same purpose, but I prefer that substantially of the type illustrated, asit leaves a desirable flat portion 22,.at the center in the plane of rotation and which is especially convenient and efficient for securing the propeller in operative position to its seat or attaching flange.

In this modification, the portion of the blades 7-5, and 8-6, has the same twist, contour, edges and dimensions as in the case of the other form, and there is likewise preferably a continuation of the leading edge of each blade with the trailing edge of the other.

In Figs. 8 to 11, the attaching means for securing the propeller in operative position in connection with thedrive-shaft 11, are shown in modified forms. In Figs. 8 to 10, the tubular attaching member 12, has an annular attaching flange 13, the device being the same as that previously described, except the flange is circular, instead of oblong, and has a circle of bolt-holes 14, corresponding with a similar series of bolt-holes formed in the flat part 22, of the propeller and which register with each other and receive the attaching bolts 16. In Figs. 8 and 9, this unitary device with its bolts is all that is used, while in the construction shown in Fig. 10, there is added upon the opposite side of the propeller, a clamping disk 23, having a central perforation for the shaft and a circular row of bolt-holes for receiving the attaching bolts 16, which pass through corresponding holes in the propeller and the flange 13. The key 17, which is set in a keyway in the shaft and also in the flanged-tube 12, also takes into a keyway in the central perforation of the clampingdisk 23.

In Fig. 11, I show the use of shaft attaching parts ordinarily used in mounting wooden propellers and which comprise a reinforce the twist or bend in the metal disk 24, like the disk 23, in Fig. 10, which engages one face of the propeller, a second clamping disk 25, upon the opposite side of the propeller with a central orifice to receive the shaft and bolt-holes for receiving the bolts 16, a block of metal or other material 26, being interposed between the disk 25, and the fiat section 22, of the propeller, with the shaft 11, passing through said block, and the bolts 16, also extending throu h the same. This arrangement permits t e use of my improved propeller with the attaching devices or hubs already in use so that the same may be used and a saving thereby made in the expense of the mechanism.

It is evident that in none of the arrangements described in reference to Figs 8, 9, 10, and 11, is the attaching means required to propeller, but functions merely as an attaching means to the drive-shaft embracing the latter over suflicient of its length to allow adequate keying of the parts' The twist or bend of the metal or other material imparted during manufacture of the pro eller, for the purpose of giving the bla es the appropriate inner or hub angles necessary for helical or similar twist, perpetuates itself during all the stresses of 7 ing, solely by its inherent elastic rigidity or set, at the'angles, bends or curves imparted during manufacture or intentional adjustment. In order that such constancy.

of shape under stress may exist there must be a relation between the thickness and Width of the material and its elastic limit and other physical properties to insure constancy at the rate of rotation, thrust and the other conditions specified by the particular .,-iflight 'dutyfor which the propeller is planned. I have found that for an absorpthat the blades tion of 400 H. P., with a 10 foot propeller at 2000 R. P. M., and a pitch of fifee't, a thickness atthe bends or twisted portions of about of an inch, with a'width of 10 inches will suflice, when one uses material such as duralumin, or similar aluminum alloy, of extra tensile strength-and elastic limit. As the blades taper in thickness steadily to inch or inch, or less, at the tips 5 and 6, and also taper materially in Width outwardly toward the tips, the resulting lightening in weight towards the tips compensates for the increased radius, so may be calculated for a substantially uniform radial tension per unit'of cross-section and the aggregate of such radialtensions at the bends or twists near the axis regionmaybe regulated not to exceed the amount which the bends or twists can sustain without straightening out u'nder the duty for which the propeller is'iplanned. With my improved ropeller constructed as herein shown and escribed, many flights protracted operation in fly have been made by airplanes of usual type and dimensions for carrying several passengers and the propellers have been found to preserve their shape absolutely.

While the parts of a propeller blade near the axis more relatively slowly in the path of rotation and furnish a relatively small fraction of the total propeller thrust, nevertheless they do so contribute, provided they are of the proper shape. In the wooden propeller the exigencies of the material used, make it necessary to so expand in thickness the blade section up to 12 inches and even to 18 inches radius, noted byexamination of drawings of conventional wooden blade sections, these portions are little better than clubs and cannot materially contribute to the thrust. By my construction of the entire propeller from a plate which need not exceed one inch in thickness, at the thickest part, I' am able to obtain effective thrust at points comparatively close to the axis of rotation, say for example, nine or twelve inches therefrom, and I thus add materially to the aggregate efliciency of propellers.

that as may be readily Numerous flying tests of airplanes equipped with my propellers have demonstrated infrom about eighteen-inch radius to aboutten-inch radius, the superiority of the sections from about eighteen-inches to about thirty-six inchesto the conventional sections being material but less marked, the tapering thin sharp blade sections be-' about thirty-six inch radius, and Y thickness being supplemented by the tapering width toward the tips.

In several of the constrfuctioiis herein shown, I have indicated Y turns on a thread on the propeller shaft 11, for the fpurpose of holding the propeller on the. sha t and preventing its moving lon itudinally thereon, while the key 17, locks the two parts in fixed relation,

In the formof my propeller in which the central blade connecting portion is made flat and without bends or twists therein, as indicated at 22, this flat portion provides an eflicient and simple structure for mounting the propeller in place. 1

While the constructions referred to produce a continuation of the leading ed e of one balde with the trailing edge .0 the other, the invention is not limited to this relation of parts.

I wish to be understoodas my inventions to'the particular forms herea nut 58, which not limiting v in shown anddescribed, as it is manifest I Having thus described my invention, what I claim and desire to secure by Letters Patent is:

1.' An aeronautical propeller having blades formed of light-weight metal having a high degree of tensile strength and converging in cross-section toward the outer portions of the blades and depending partly but mainly upon centrifugal force for effective operation;

2. An aeronautical propeller having blades formed of light-weight metal, the propeller being relatively thin at its central portion and having a substantial width at said central portion to provide the necessary rigidity to resist torque, and said propeller so converging in width toward the end portions of the blades as to provide the necessary relation of form ;to weight and which blades depend substantially uponcentrifugal force for efiective operation.

3. An aeronautical propeller formed from a plate of light-weight metal in a single piece, the propeller having only the thickness of the plate at its central portion and having a substantial width at said central portion such as to provide the necessaryrigidity to resist torque, and said propeller so converging in thickness and in width toward ,the tip portions of thefblades as to provide the necessary relation-oi form to weight and which blades depend substantially upon' centrifugal force for effective 0 ration.

4. An aeronautical prope ler formed of. light-weight metal, the ropeller being rela-I tively wi e at its centre portion to provide the necessary rigidity to resist torque, the

said propeller converging progressivel incross-section toward t e tip ortions o the blades to such a degree as to orrn relatively non-rigid end portions depending substantially upon the effect of centrifugal force to provide the necessary degree of rigidity for efficient operation.

5. An aeronautical propeller havingblades formed of duralumm or an alloy having substantially the hysical characteristics thereof and said bla es being of such thin ness that the structural rigidity due to :material and shape is not sufficient to produce the total rigidity'which is necessary to overcome the resistances in operation but has to be supplemented for anessential part by'the kinetic rigidity resulting from the centrifugal force. y f

6. An aeronautical propeller consisting of a single-piece forging of duralumin or an alloy having substantially the physical characteristics thereof and having a relatively substantial width at the central portion and the blades converging in width toward the end portions.

. .7. An aeronautical propeller consisting of a single forged plate of duralumin or an alloy having substantially the physical blades formed of "forged a 0:7 of alumi- -to provide stability against tangential deflection due to torque, said light-weight metal possessing an inhejrent rigidity which combined Withthe form of the blades provides stability of pitch. 7

9. An aeronautical propeller formed of light-weight metal with a thin cross-section throughout its length and progressively decreasing in cross-section toward the outer extremities of the blades to provide a thin and sharp-edged construction and to rely for stability against axial deflection substantially upon centrifugal force, and being comparatively thin and wide at or near the axis to ,provide stability a ainst tangential deflection due to torque o 'the driveshaft, saidglfight-weight metal having sufficient inherent rigidity when "combined vjith the form of the blades to provide stability of pitch when operating at high "rotative speeds. I

" 10. An aeronautical propellenmade from a single piece' of ligh'tV -weightjmetal flat and thin'throughout and with the blades united by a reversing formation and in ice" which the thickness, aiid width ofzthe axial zone .is so adjusted to the physical properties of the material 'used and the stresses [of service,that central angle-reversing formation will persist without reinforce mentduring such service, and whose-blades depend partly but mainly upon centrifugal forte for eflective operation.

lid

11. An aeronautical ,pro eller 'having blades formed of an alloy 0 aluminum.

12. An aeronautical propeller" having blades formed of 'du'ralumim 13. An aeronautical pro ller having 14:. aeronautical propeller 1 0Vl,dl8d with blades formed of ight-wei'g t metal -havin a relatively high tensile strength,

metal blades converging in width and thickness toward the outer ends, said blades possessing a substantial degree of rigidity but the degree of convergence being such as to re uire the supplemental stiffening 'ac tion dl centrifugal orce for operation.

16. An aeronautical propeller having blades formed of light-weight metal having a high degree of tensile strength saidblades eonvergin in cross-section toward theouter portions t ereof and depending upon cen- 21stday of June A. D. 1922.

SYLVANUS ALBERT REED. 

